Flap wheels include discrete packs of abrasive or polishing sheet materials which are mounted in a rotary hub in turn mounted on a power driven arbor. Some packs are hinged to the hub while others fit in slots in the periphery, which slots are usually axial or slightly helical.
The packs are preassembled and mounted in clips which in turn fit in the slots or which are hinged to the hub. The clips are typically provided with relatively thin projecting side walls and the pack components are held to each other and to the clips by fasteners such as staples which extend through the side walls and the inner edge of the pack components embraced by the walls.
Because of the fasteners the walls of the clip normally project beyond the slots in the hub. An example of a flap pack and clip assembly fitting in a hub slot may be seen in applicants prior U.S. Pat. No. 6,592,442 B2.
In operation the tool is rotated with some pressure against the work being abraded or finished and the packs are the wear replacement parts. When worn the tool is disassembled and the old worn packs are removed and replaced by new packs. The end plates are removed and the worn packs are slid out of the slots, new packs are inserted into the slots, and the end plates are replaced. The amount of time the tool is down and the time and effort it takes to remove and replace the packs is important to the productivity of the tool.
That the packs be easily slid in and out of the slots is important to facilitate and reduce the amount of time a replacement requires. Also, because of the normal manufacturing tolerances in the manufacture of the packs, the clearance between the slot and pack can't be too close, otherwise disassembly and assembly would be inordinately slow and may even require special tools. It is primarily for this reason that there is a fairly wide tolerance between the slot and pack-clip assembly.
Unfortunately this tolerance creates a vibration of the pack within the slot when the tool is in use and being pressed against the work. This is in part caused by the fact that the pack engages the work once per revolution and when not engaging the work centrifugal force tends to straighten out the pack creating a relatively high frequency vibration.
It has been found with testing that this vibration tends to create stress fractures in the metal pack clip, particularly near the confining slot of the hub outer corners.
Extending the slot radially to embrace more of the clip to provide better support is not practical because of the fasteners or staples extending through the clip walls which tend to project in an irregular fashion. It would however be desirable if the vibrations of the packs within the slots could be dampened without affecting the tolerance and the ease of assembly and disassembly of the hub and packs. This would increase the useful life of the packs while not increasing the time or effort needed for pack replacement.